PARASITES — SCHWARTZ 425 



the serious nature of the disease it can produce, has focused attention 

 on trichinosis during the past two decades to such an extent that much 

 of the valuable data brought to light by numerous survey studies some- 

 times has been misconstrued and misinterpreted. The evidence at 

 hand indicates that one out of six persons, whose muscles were ex- 

 amined postmortem by special techniques that bring to light even 

 very small numbers of trichinae, showed for the most part a light 

 infection with this nematode. There was little or nothing, however, 

 in the medical histories of individuals so infected to indicate that they 

 had suffered from trichinosis during life, even including those in whose 

 muscles relatively large numbers of worms were found. Such vague 

 symptoms as muscular pain or rheumatism recorded in the medical 

 histories of some of the affected persons also were found in those of 

 individuals who were free of trichinae. 



The wide prevalence of trichinae in our human population certainly 

 affords evidence that pork is a popular item in our diet; that some of 

 the hogs in this country contain trichinae; and that we sometimes, 

 probably many times in the course of our lives, eat pork that has not 

 been sufficiently processed by heat or in other ways to destroy the vital- 

 ity of all the live trichinae it may have contained. 



So far as known, about two-thirds of 1 percent of our farm-raised 

 hogs are infected with trichinae, and the intensity of the infection 

 apparently is very low. In very few of the infected hogs involved 

 in studies in the Agricultural Research Service of the United States 

 Department of Agriculture could the parasites be demonstrated by 

 the direct examination of two or three microscopic preparations of 

 muscle tissue taken from the pillars of the diaphragm. In garbage- 

 fed hogs, on the other hand, the incidence of infection with trichinae 

 varied considerably and reached in some cases nearly 12 percent of 

 those examined. The nimibers of trichinae present in about half of 

 the hogs so affected were large enough to be readily demonstrable in 

 microscopic preparations of muscle tissue. In the last two years, 

 however, most of the States have passed legislation requiring the cook- 

 ing of garbage to check the spread of a virus disease of swine known 

 as vesicular exanthema. This cooking has already been reflected in a 

 vei-y sharp reduction in the incidence of trichinae in the hogs fed this 

 garbage. 



From the data at hand it may be concluded, therefore, that the more 

 serious or clinical cases of trichinosis are acquired for the most part 

 from infected pork obtained from hogs fed uncooked garbage. The 

 nonclinical or zoological trichinosis in man, which has been so widely 

 publicized, is acquired apparently from uncooked pork obtained from 

 farm-raised hogs in which trichinae occur as a rule in very small 

 numbers. "When we consider the fact that pork is one of the com- 



